enhance(docker): add healthcheck to execution + conditional depends_on for node

[lau90eth]

What this PR does / Why we need it:

Currently, depends_on: [execution] only waits for the container to start, not for the execution client (Geth/Reth) to be fully ready (e.g., RPC responding). This often causes op-node to crash or loop on startup with "execution RPC not ready" errors.

This PR fixes it with Docker Compose best practices:

• Adds a simple healthcheck to execution service (curl on internal metrics endpoint 6060).
• Changes depends_on in node to condition: service_healthy.

Changes:

• Added healthcheck block to execution:

  healthcheck:
    test: ["CMD", "curl", "-f", "http://localhost:6060"]
    interval: 30s
    timeout: 10s
    retries: 5
    start_period: 60s
    
    Updated node depends_on:YAML
    depends_on:
  execution:
    condition: service_healthy
    
    Verification (tested locally on WSL2 + Docker Desktop):
  

docker compose config → Valid YAML.
docker compose up -d --build → Services start; execution becomes "healthy" after init.
docker compose ps: execution shows health status; node waits properly.
No crashes from premature op-node startup.

References:

Docker Compose docs: https://docs.docker.com/compose/compose-file/05-services/#healthcheck
https://docs.docker.com/compose/compose-file/05-services/#dependson (condition: service_healthy)

Open to tweaks (e.g., different test endpoint like 8545 RPC, adjust timings). Thanks for reviewing!

[cb-heimdall]

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[Dark-Brain07]

Great addition! The healthcheck approach using the metrics endpoint (port 6060) is solid.
One suggestion: consider documenting this in the README troubleshooting section - we recently added a troubleshooting guide for Geth (PR #933) that mentions startup timing issues. This healthcheck fix would pair nicely with that documentation.
Also worth noting: the start_period: 60s might need adjustment for archive nodes which take longer to initialize.